1. Field of the Invention
The invention relates to an improved disk brake with self-boosting.
2. Description of the Prior Art
Disk brakes are known that have a friction brake lining, which for braking can be pressed by an actuation unit against a brake disk, and a self-boosting device which converts a frictional force, which the rotating brake disk upon braking exerts on the friction brake lining pressed against it, into a contact-pressure force, that in addition to the actuation unit presses the friction brake lining against the brake disk. As a result, a contact-pressure force to be exerted by the actuation unit is reduced and self-boosting is attained.
Mechanical self-boosting devices with wedge mechanisms or lever systems are known. The wedge mechanisms are also known as ramp mechanisms. This list is not exhaustive. Wedge mechanisms have a wedge on a back side of the friction brake lining, remote from the brake disk, that is braced on a counterpart wedge. The counterpart wedge is typically fixedly disposed in a brake caliper of the disk brake. The counterpart wedge forms a bracing means for the friction brake lining, on which the friction brake lining in braking is braced at a support angle obliquely to the brake disk. The wedge angle and support angle are typically of equal size.
If the friction brake lining for braking is pressed by the actuation unit against the rotating brake disk, the frictional force exerted by the rotating brake disk on the friction brake lining pressed against it displaces the friction brake lining in the direction of a narrowing wedge gap between the counterpart wedge and the brake disk. As a force of reaction, the counterpart wedge exerts a force on the wedge that has one component transverse to the brake disk. This force transverse to the brake disk is an additional contact-pressure force, which in addition to the actuation unit presses the friction brake lining against the brake disk and as a result increases the total contact-pressure force, resulting in the self-boosting.
In the case of lever mechanisms, the friction brake lining in braking is braced on a lever that is oblique to the brake disk at a support angle. The support angle corresponds to the wedge angle in the wedge mechanism; both mechanisms are mechanically comparable to one another, with the special feature that the support angle of a lever mechanism can change, and if no countermeasure is taken, it does in fact change.
Still other self-boosting systems, for instance hydraulic ones, are also known.
The problem exists that a displacement travel distance, by which distance the friction brake lining must be displaced in order to actuate the disk brake until it rests on the brake disk, increases with increasing wear of the friction brake lining.